1. Field of the Invention
This invention relates to apparatus for converting digital electrical signals representing characters into particular self-locking patterns of dots. Each of these characters is symbolized by a dot pattern represented by projections which project from a given surface and which are related to a given number of dots lying in a predetermined grid and characteristic of a Braille code.
2. Description of the Prior Art
A typical representation of characters by means of a grid of dots is the code invented by Braille. The Braille code is a universal means of communication particularly well suited to use by the blind. All the characters and symbols in the Braille system correspond to respective particular patterns of projecting dots in a grid consisting of six dots.
It will apparent from the following description that the invention can be adapted to other applications, but the example which will be used to illustrate the invention will be based on the Braille alphabet.
Conventional arrangements for converting digital electrical signals representing characters to the Braille format are well known. In a typical data processing system, the digital signals from the processing source appear in a coded form, such as the octal coded form, and are processed by a transcoder which converts them to the Braille format as six-bit signals to allow the characters to be formed. Each of the six output channels from the transcoder is connected to an individual electromechanical member which causes a rod to project from the reading surface as a result of the said member being energized. The member may be energized when it receives a predetermined energizing level signal, for example, corresponding to the logic "1" level.
With this type of energization, the rods only project for the length of time during which the corresponding electromechanical members are energized. In the general case where the transcoded electrical signals are transient, but the reader requires the information to persist for a period of time which is relatively long compared with the transcoded signals, existing converting arrangements generally include a hold-in device connected between the transcoder and the electromechanical members to maintain the data in a read condition. In addition, a clearing member operated by the blind person serves to cancel out the information. Where it is necessary that the electromechanical members which are selected to present each character should remain energized for as long as the blind person requires, the addition of a hold-in member requires a consumption of energy which increases as the number of Braille producing modules on the blind person's reading panel increases.